Emerging Concepts in the Treatment of Intracranial Aneurysms: Stents, Coated Coils, and Liquid Embolic Agents

Biocompatible Liquid Embolic for the Treatment of Microvascular Hemorrhage

Persistent or recurrent bleeding from microvessels inaccessible for direct endovascular intervention is a major problem in medicine today. Here, an innovative catheter-directed liquid embolic (P-LE) is bioengineered for rapid microvessel embolization to treat small vessel hemorrhage. Tested in rodent, porcine, and canine animal models under normal and coagulopathic conditions, P-LE outperformed clinically used embolic materials in both survival and non-survival experiments, effectively occluding vessels as small as 40 microns with no signs of recanalization. P-LE occlusion is independent of the coagulation cascade, and its resistance to displacement is ≈ 8 times greater than systolic blood pressure. P-LE is also found to be biocompatible and x-ray visible and does not require polymerization or a chemical reaction to embolize. To simulate the clinical scenario, acute microvascular hemorrhage is created in the pig kidney, liver, or stomach; these are successfully treated with P-LE achieving immediate hemostasis. Furthermore, P-LE is found to be bactericidal to highly resistant patient-derived bacteria, suggesting that P-LE may also protect against infectious complications that may occur following embolization procedures. P-LE is safe, easy to use, and effective in treating -microvessel hemorrhage.

Classification and microsurgical treatment of foramen magnum meningioma

BACKGROUND

To investigate the classification and microsurgical treatment of foramen magnum meningioma (FMM).

METHODS

We retrospectively analyzed 76 patients with FMM and classified them into two classifications, classification ABS according to the relationship between the FMM and the brainstem and classification SIM according to the relationship between the FMM and the vertebral artery (VA). All patients underwent either the far lateral approach (54 cases) or the suboccipital midline approach (22 cases).

RESULTS

Of the 76 cases, 47 cases were located ahead of the brainstem (A), 16 cases at the back of the brainstem (B), and 13 cases were located laterally to the brainstem (S). There were 15 cases located superior to the VA (S), 49 cases were inferior (I), and 12 cases were mixed type (M). Among 76 cases, 71 cases were resected with Simpson grade 2 (93.42%), 3 with Simpson grade 3 (3.95%), and 2 with Simpson grade 4 (2.63%). We summarized four anatomical triangles: triangles SOT, VOT, JVV, and TVV. The mean postoperative Karnofsky performance score was improved in all patients (p < 0.05). However, several complications occurred, including hoarseness and CSF leak.

CONCLUSION

ABS and SIM classifications are objective indices for choosing the surgical approach and predicting the difficulty of FMMs, and it is of great importance to master the content, position relationship with the tumor, and variable anatomical structures in the four "triangles" for the success of the operation.

Photosensitive Hydrogel-Based Embolic Agent Treatment of Wide-Necked Aneurysms: Preliminary Animal Results

Background: The endovascular treatment of cerebral aneurysms has become widespread but may still be limited by recurrence rates or complications. The discovery of novel embolic strategies may help mitigate these concerns. Methods: We formulated a Photosensitive Hydrogel Polymer (PHP) embolic agent which is low-viscosity, shear-thinning, and radio-opaque. After the filling of an aneurysm with PHP with balloon assistance, we utilized photopolymerization to induce solidification. Different methods of light delivery for photopolymerization were assessed in silicone models of aneurysms and in four acute animal trials with venous anastomosis aneurysms in pigs. Then, balloon-assisted embolization with PHP and photopolymerization was performed in three aneurysms in pigs with a one-month follow-up. Filling volume, recurrence rates, and complications were recorded. Results: The PHP was found to be suitable for the intravascular delivery and treatment of cerebral aneurysms. It was found that light delivery through the balloon catheter, as opposed to light delivery through the injection microcatheter, led to higher rates of filling in the 3D model and acute animal model for cerebral aneurysms. Using the balloon-assisted embolization and light delivery strategy, three wide-necked aneurysms were treated without complication. One-month follow-up showed no recurrence or neck remnants. Conclusions: We demonstrated a novel method of balloon-assisted photosensitive hydrogel polymer embolization and photopolymerization, leading to complete aneurysm filling with no recurrence at 1 month in three wide-necked aneurysms in pigs. This promising methodology will be investigated further with longer-term comparative animal trials.

Initial and mid-term results of LEO Baby stent-assisted coiling of intracranial aneurysms located in small arteries: A single-center experience with 131 consecutive patients

Background and purpose

Low-profile intracranial stents such as the LEO Baby stents are considered to be advantageous for the treatment of intracranial aneurysms originating from small arteries. This study aimed to evaluate the initial and mid-term clinical and angiographic results of LEO Baby stents in stent-assisted coiling of intracranial aneurysms with small parent arteries (<2.5 mm).

Methods

We performed a retrospective study to identify 131 patients with aneurysms arising from small parent arteries treated with Leo Baby stent-assisted coiling in a single institution between October 2018 and June 2021. We assessed the immediate and progressive aneurysm occlusion rates, procedure-related complications, and clinical outcomes.

Results

A total of 131 patients with 135 aneurysms were identified, including 65 (48.1%) cases of acutely ruptured aneurysms. Technical success was achieved in all cases (100%). The immediate angiography showed complete occlusion in 111 aneurysms (82.2%), neck remnants in 19 (14.1%), and residual sac in 5 (3.7%). Procedure-related complications occurred in 14 cases (10.3%), including 13 (9.6%) thromboembolic complications and 1 (0.7%) hemorrhagic complication. Six-month follow-up angiography was achieved in 106 (78.5%) aneurysms, which showed complete occlusion in 102 (96.2%) aneurysms, neck remnants in 2 (1.9%), and residual sac in 2 (1.9%). Clinical follow-up was available in all patients with a median duration of 6.8 months, and favorable clinical outcomes (modified Rankin Scale score: 0–2) reached 91.6%. The mortality rate was 4.6%.

Conclusion

Our results demonstrate that stent-assisted coiling of intracranial aneurysms located on small arteries using LEO Baby stents is technically feasible, highly effective, and has midterm durability in aneurysmal occlusion.

Treatment of Ruptured and Nonruptured Aneurysms Using a Semisolid Iodinated Embolic Agent

Saccular aneurysms (SAs) are focal outpouchings from the lateral wall of an artery. Depending on their morphology and location, minimally invasive treatment options include coil embolization, flow diverter stents, stent-assisted coiling, and liquid embolics. Many drawbacks are associated with these treatment options including recanalization, delayed healing, rebleeding, malpositioning of the embolic or stent, stent stenosis, and even rupture of the SA. To overcome these drawbacks, a nanoclay-based shear-thinning hydrogel (STH) is developed for the endovascular treatment of SAs. Extensive in vitro testing is performed to optimize STH performance, visualization, injectability, and endothelialization in cell culture. Femoral artery saccular aneurysm models in rats and in pigs are created to test stability, efficacy, immune response, endothelialization, and biocompatibility of STH in both ruptured and unruptured SA. Fluoroscopy and computed tomography imaging consistently confirmed SA occlusion without recanalization, migration, or nontarget embolization; STH is also shown to outperform coil embolization of porcine aneurysms. In pigs with catastrophic bleeding due to SA rupture, STH is able to achieve instant hemostasis rescuing the pigs in long-term survival experiments. STH is a promising semisolid iodinated embolic agent that can change the standard of medical practice and potentially save lives.

Computational Study of Hemodynamic Changes Induced by Overlapping and Compacting of Stents and Flow Diverter in Cerebral Aneurysms

Purpose: The flow diversion effect of an intracranial stent is closely related to its metal coverage rate (MCR). In this study, the flow diversion effects of Enterprise and low-profile visualized intraluminal support (LVIS) stents are compared with those of a Pipeline flow diverter, focusing on the MCR change. Moreover, the changes in the flow diversion effect caused by the additional manipulations of overlapping and compaction are verified using computational fluid dynamics (CFD) analysis. Methods: CFD analysis was performed using virtually generated stents mounted in an idealized aneurysm model. First, the flow diversion effects of single Enterprise, LVIS, and Pipeline devices were analyzed. The Enterprise and LVIS were sequentially overlapped and compared with a Pipeline, to evaluate the effect of stent overlapping. The effect of compacting a stent was evaluated by comparing the flow diversion effects of a single and two compacted LVIS with those of two overlapped, uncompacted LVIS and uncompacted and compacted Pipeline. Quantitative analysis was performed to evaluate the hemodynamic parameters of energy loss, average velocity, and inflow rate. Results: Statistically significant correlations were observed between the reduction rates of the hemodynamic parameters and MCR. The single LVIS without compaction induced a reduction in all the hemodynamic parameters comparable to those of the three overlapped Enterprise. Moreover, the two overlapped, uncompacted LVIS showed a flow diversion effect as large as that induced by the single uncompacted Pipeline. Compacted stents induced a better flow diversion effect than uncompacted stents. The single compacted LVIS induced a flow diversion effect similar to that induced by the two uncompacted LVIS or single uncompacted Pipeline. Conclusions: The MCR of a stent correlates with its flow diversion effect. Overlapping and compaction can increase the MCR of an intracranial stent and achieve a flow diversion effect as large as that observed with a flow diverter.

Case history on Epstein-Barr Virus-associated smooth muscle tumor (EBV-SMT) of cranio-cervical junction in an immunocompetent patient

Epstein-Barr virus-associated smooth muscle tumor (EBV-SMT) is a rare mesenchymal tumor that almost exclusively occurs in immunocompromised hosts. Here, we report a 75-year-old Taiwanese woman without definite immune-deficient history presenting with progressive occipital neuralgia, low cranial nerve deficits (CN9-12) and cervical (C1-C5) radiculopathy. Magnetic resonance imaging revealed a 4.5*4.0*6.7 cm infiltrating mass occupying posterior skull base and C1-C2 vertebra and C1-5 epidural extension with bone destruction and vertebral artery (VA) encasement. There was also a synchronous 2.7 cm tonsillar tumor. A two-stage operation for cranio-cervical tumor excision and stabilization was performed. Tumor was confirmed directly arising from VA intraoperatively. Pathology reported a spindle cell neoplasm and the diagnosis of EBV-SMT was confirmed by EBER (EBV-encoded small RNA) in situ hybridization. An immune survey and reconstruction should be conducted for patient with EBV-SMT. A near-total resection of tumor may be beneficial for local control, however, the role of surgical resection in treating CNS EBV-SMT remains to be determined.

Endovascular Treatment of Intracranial Aneurysms

Traditionally, surgical clipping was the only available treatment modality for intracranial aneurysms. However, in the last few decades, the endovascular therapy of intracranial aneurysms (IAs) has seen a tremendous evolution and development. From coiling to flow diversion and flow disruptor devices, endovascular treatment modalities have increased in number and received broader indications throughout the years. In this review article, the treatment modalities for the endovascular management of IAs are presented, emphasizing newer devices and technologies.

Advances in Biomaterials and Technologies for Vascular Embolization

Minimally invasive transcatheter embolization is a common nonsurgical procedure in interventional radiology used for the deliberate occlusion of blood vessels for the treatment of diseased or injured vasculature. A wide variety of embolic agents including metallic coils, calibrated microspheres, and liquids are available for clinical practice. Additionally, advances in biomaterials, such as shape-memory foams, biodegradable polymers, and in situ gelling solutions have led to the development of novel preclinical embolic agents. The aim here is to provide a comprehensive overview of current and emerging technologies in endovascular embolization with respect to devices, materials, mechanisms, and design guidelines. Limitations and challenges in embolic materials are also discussed to promote advancement in the field.

Device thrombosis and pre-clinical blood flow models for assessing antithrombogenic efficacy of drug-device combinations

Thrombosis associated with blood-contacting devices is a complex process involving several component interactions that have eluded precise definition. Extensive investigations of individual biological modules such as protein adsorption, coagulation cascade activation and platelet activation/adhesion/aggregation have provided an initial foundation for developing biomaterials for blood-contacting devices, but a material that is intrinsically non-thrombogenic is yet to be developed. The well-recognized association between fluid dynamics parameters such as shear stress, vortices, stagnation and thrombotic processes such as platelet aggregation and coagulation aggravate thrombosis on most device geometries that elicit these flow disturbances. Thus, antithrombotic drugs that were developed to treat thrombosis associated with vascular diseases such as atherosclerosis have also been adapted to mitigate the risk of device thrombosis. However, balancing the risk of bleeding with the antithrombotic efficacy of these drugs continues to be a challenge, and surface modification of devices with these drug molecules to mitigate device thrombosis locally has been explored. Pre-clinical blood flow models to test the effectiveness of these drug-device combinations have also evolved and several in-vitro, ex-vivo, and in-vivo test configurations are available with their attendant merits and limitations. Despite considerable efforts toward iterative design and testing of blood contacting devices and antithrombogenic surface modifications, device thrombosis remains an unsolved problem.

Halting hemorrhage with self-propelling particles and local drug delivery

Approaches to locally deliver drugs to specific regions of the body are being developed for many clinical applications, including treating hemorrhage. Increasing the concentration of therapeutic coagulants in areas where clots are forming and growing can be achieved by directing them to the injury, such as with catheters or external delivery devices, or by systemically administering therapeutics that target molecular signals of vascular damage. Treating severe hemorrhage by external measures is challenging because blood flow pushes hemostatic agents outward, reducing their efficacy. This review explains that self-propelling particles may be used for delivering therapeutics, such as coagulation factors, small molecules, or other chemical or biological agents, deep into wounds during hemorrhage. A recent example of self-propelling particles is highlighted, where propulsion enhanced the efficacy of a formulation of thrombin and tranexamic acid in treating bleeding in two murine models of hemorrhage and a porcine model of fatal, non-compressible hemorrhage. Many agents exist which modulate clotting, and novel approaches that facilitate their safe delivery to sites of vascular injury could reduce the enormous number of deaths from hemorrhage that occur globally.

[Endovascular treatment of large and giant intracranial aneurysms using stent assistance]

OBJECTIVE

The study objective was to evaluate the efficacy of occlusions of large and giant intracranial aneurysms with microcoils using stent assistance (SA).

MATERIAL AND METHODS

The study is based on analysis of treatment outcomes in 37 patients with large (15-25mm) and giant (more than 25mm) intracranial aneurysms, aged 18 to 72 years, who were hospitalized at the Burdenko Neurosurgical Institute in the period between 2004 and 2014. Selection of patients for endovascular treatment using SA was based on the anatomical parameters of the aneurysm and carrier vessel. The main determining factor was the index of the aneurysm body to neck size ratio. Occlusion of aneurysms was performed with microcoils of different configurations, including those with a biologically active coating. Self-expanding stents with both an open-cell and closed-cell design were used for SA. The results of intervention for large and giant aneurysms were evaluated using control angiography immediately after occlusion of the aneurysm. The condition of patients with unruptured aneurysms as well as with ruptured aneurysms in the "cold" period was evaluated using the modified Rankin scale. The condition of patients in the acute period of SAH was evaluated on the Hunt and Hess scale.

RESULTS

The technical success (successful implantation of stents and coils with total or subtotal aneurysm occlusion) was 94.5%. The postoperative disability was 2.7%; mortality was 2.7%. 28 patients were followed up for the period of 5 to 84 months (the mean was 20 months.). In the long-term period, the total and subtotal occlusion rate, including the results of re-operations, amounted to 90%. Delayed disability was 10.7%, and mortality was 3.5%.

CONCLUSION

Stent assistance enables achieving total or subtotal occlusion of large and giant aneurysms in 90% of cases. In certain clinical situations, it is an alternative to other existing methods.

Intervention in HCM: patient selection, procedural approach and emerging techniques in alcohol septal ablation

Hypertrophic cardiomyopathy (HCM) is a highly heterogeneous disease with varied patterns of hypertrophy. Basal septal hypertrophy and systolic anterior motion (SAM) of the mitral valve (MV) are the key pathophysiological components to left ventricular outflow tract (LVOT) obstruction in HCM. LVOT is associated with higher morbidity and mortality in patients with HCM. Percutaneous septal reduction therapy with alcohol septal ablation (ASA) can lead to a significant improvement in left ventricle haemodynamics, patient symptoms and perhaps prognosis. ASA delivers pure alcohol to an area of myocardium via septal coronary arteries; this creates damage to tissue akin to a myocardial infarction. The basal septal myocardium involved in SAM-septal contact is the target for this iatrogenic infarct. Appropriate patient selection and accurate delivery of alcohol are critical to safe and effective ASA. Securing the correct diagnosis and ensuring suitable cardiac anatomy are essential before considering ASA. Pre-procedural planning and intra-procedural imaging guidance are important to delivering precise damage to the desired area. The procedure is performed worldwide and is generally safe; the need for a pacemaker is the most prominent complication. It is successful in the majority of patients but room for improvement exists. New techniques have been proposed to perform percutaneous septal reduction. We present a review of the relevant pathophysiology, current methods and a summary of available evidence for ASA. We also provide a glimpse into emerging techniques to deliver percutaneous septal reduction therapy.

Polymeric embolization coil of bilayered polyvinyl alcohol strand for therapeutic vascular occlusion: a feasibility study in canine experimental vascular models

PURPOSE

To investigate the feasibility of polyvinyl alcohol (PVA) polymer coil as a new endovascular embolic agent and to gauge the related histologic response in a canine vascular model.

MATERIALS AND METHODS

PVA polymer coil was fabricated by cross-linking PVA and tantalum particles. Basic properties were then studied in vitro via swelling ratio and bending diameter. Normal renal segmental arteries and wide-necked aneurysms of carotid sidewalls served as canine vascular models. Endovascular PVA coil embolization of normal renal segmental arteries (N = 20) and carotid aneurysms (N = 8) was performed under fluoroscopic guidance in 10 dogs. Degree of occlusion was assessed immediately and at 4 weeks after embolization by conventional and computed tomographic angiography. Histologic features were also graded at acute (day 1, six segmental arteries and four aneurysms) and chronic phases (week 4, 14 segmental arteries and four aneurysms) after embolization to assess inflammation, organization of thrombus, and neointimal proliferation.

RESULTS

Swelling ratio declined as concentrations of cross-linking agent increased. Mean bending diameters were 2.05 mm (range, 0.86-6.25 mm) in water at 37 °C and 2.29 mm (range, 0.94-6.38 mm) in canine blood samples at 37 °C. Occlusion of normal renal segmental arteries was sustained (complete occlusion at day 1, n = 20; at week 4, n = 14), whereas immediate outcomes in carotid aneurysms (day 1, complete occlusion, n = 5; residual neck only, n = 3) were not sustained (week 4, complete occlusion, n = 1; minor recanalization, n = 1; major recanalization, n = 2). At week 4, chronic inflammatory cells predominated, with progressive organization of thrombus and fibrocellular ingrowth. All aneurysms bore full neointimal linings on the coil mass in the chronic phase.

CONCLUSIONS

Vascular occlusion by PVA polymer coil proved superior in normal renal segmental arteries and feasible in surgically constructed carotid aneurysms (with packing densities ≥ 30%), constituting acceptable radiologic feasibility and histologic response.

Hemodynamic impact of cerebral aneurysm endovascular treatment devices: coils and flow diverters

Coils and flow diverters or stents are devices successfully used to treat cerebral aneurysms. Treatment aims to reduce intra-aneurysmal flow, thereby separating the aneurysmal sac from the blood circulation. The focus and this manuscript combining literature review and our original research is an analysis of changes in aneurysmal hemodynamics caused by endovascular treatment devices. Knowledge of post-treatment hemodynamics is a path to successful long-term treatment. Summarizing findings on hemodynamic impact of treatment devices, we conclude: coiling and stenting do not affect post-treatment intra-aneurysmal pressure, but significantly alter aneurysmal hemodynamics through flow reduction and a change in flow structure. The impact of treatment devices on aneurysmal flow depends, however, on a set of parameters including device geometry, course of placement, parent vessel and aneurysm geometry.

Stent-assisted coiling versus coiling in treatment of intracranial aneurysm: a systematic review and meta-analysis

Background and Purpose

Stent-assisted coiling was initially invented for wide-neck aneurysms, but is now used for smaller berry aneurysms. The aim of this study was to compare the safety and efficiency of stent-assisted coiling with conventional coiling in treatment of intracranial aneurysms.

Methods

A meta-analysis of studies that compared stent-assisted coiling with coiling only was conducted by searching English literatures via Pubmed, Medline and Cochrane Library databases without restricting the publication year. The primary outcomes in this study were immediate occlusion, progressive thrombosis rate, all-complication rate and angiographic recurrence. The secondary outcomes examined were packing density, mortality, permanent complication and thromboembolic complication rate.

Results

Ten retrospective cohort studies were included. There is currently only one unfinished randomized study. Although the stent-assisted coiling group tended to show a lower initial occlusion rate than that of the coiling-only group (57.6% versus 68.7%; OR, 0.66; 95% CI, 0.30–1.44; P = 0.30), it achieved a significantly higher progressive thrombosis rate during follow up compared to that of the coiling only group (37.5% versus 19.4%; OR, 2.75; 95% CI, 1.95–3.86; P<0.00001) and a significantly lower recurrence rate (16.2% versus 34.4%; OR, 0.35; 95% CI, 0.25–0.49; P<0.00001). With respect to safety concerns, the all-complication rate (17.6% versus 15.9%; OR, 1.12; 95% CI, 0.77–1.62; P = 0.56), mortality rate (9.1% versus 2.6%; OR, 2.31; 95% CI, 0.68–7.82; P = 0.18), permanent complication rate (5.6% versus 3.9%; OR, 1.52; 95% CI, 0.96–2.41; P = 0.08) and thromboembolic complication rate (4.2% versus 4.9%; OR, 0.99; 95% CI, 0.41–2.38; P = 0.97) did not show significant difference between the two groups.

Conclusions

Stent-assisted coiling has a lower recurrence rate than conventional coiling. Analysis of complication events did not show any significant difference between the two methods. Despite the findings reported herein, further validation by well-designed prospective studies is needed.

Endovascular remodeling of tortuous cervical segments of the internal carotid artery that hinder the management of complex intracranial aneurysms

Introduction: Severe tortuosity of the cervical segment of the internal carotid artery (ICA) may hamper the navigation of intravascular devices for the management of complex intracranial aneurysms and even conventional techniques of ICA access can fail. In a group of selected cases, we analyzed the efficacy and safety of carotid stenting to straighten the Severe tortuosity for direct navigation of the devices. Methods: A case series of 16 patients harboring 18 intracranial aneurysms with a difficult endovascular approach because of a cervical ICA with Severe tortuosity were prospectively recruited at our institution from January 2005 to December 2007. When traditional means of correction could not surmount this obstacle, an overlap stenting with a distal-to-proximal technique was used to overcome the Severe tortuosity. The efficacy of the procedure was defined as the ability to reach and be able to treat the target lesion with a smooth navigation of the endovascular devices. Safety was documented by procedure-related complications. Results: The straightening of the vessel by the stent helped to overcome pitfalls, making possible an obstacle-free navigation of the endovascular devices to the target lesion in all cases. In 5 cases with severe or double kinking, a distal transfer of the curve beyond the stent was observed, without impact on the efficacy of the procedure. One case of periprocedural related technical complication occurred with a permanent stroke. During the follow-up period (22.7 ± 8.4 months) no case of stent-related stroke or severe hyperplasia was observed. Conclusions: Carotid stenting is an available option when a cervical ICA with Severe tortuosity hampers a smooth catheterization of the intracranial circulation, in carefully selected cases. It allows a relatively safe and free navigation and/or deployment of additional endovascular devices needed for the treatment of complex intracranial aneurysms.

Flow Diversion for Intracranial Aneurysms

The introduction of flow diverters for treatment of intracranial aneurysms represents a major paradigm shift in the treatment of these lesions. The theoretical hallmark of flow diverters is the treatment of the diseased segment harboring the aneurysm instead of treating the aneurysm itself. Flow diverters are designed to induce disruption of flow near the aneurysm neck while preserving flow into parent vessel and adjacent branches. After flow diversion, intra-aneurysmal thrombosis occurs, followed by shrinkage of the aneurysmal sac as the thrombus organizes and retracts. Preliminary clinical series document effective treatment of wide-neck and/or large and giant aneurysms with acceptable complication rates. However, several questions remain unanswered related to the incidence and mechanisms of aneurysm rupture after treatment with flow diverters, fate of small perforating vessels, and long-term patency rates.

Flow diversion in aneurysms trial: the design of the FIAT study

Intracranial aneurysms, particularly large and giant, fusiform or recurrent aneurysms are increasingly treated with flow diverters (FDs), a recently introduced and approved neurovascular device. While some rare cases may not be treated any other way, in most patients a more conventional, conservative, or validated approach such as coiling, parent vessel occlusion, or surgical clipping exists. Only a randomized clinical trial can answer the question of which treatment option leads to better patient outcomes.We report the design of the FIAT study, a clinical care trial aiming to compare angiographic and clinical outcomes following treatment with a Flow-Diverter or with the best conventional treatment option. The FIAT study will include both a randomized and a registry portion. Patients will be proposed randomization to either FD stenting or best conventional treatment option (observation, coiling, stenting, or clipping) as determined by the treating physician. FIAT will recruit a total of 338 patients, to show that i) FD stenting can be performed with an 'acceptable' immediate complication rate of less than 15% morbidity and mortality (defined as mRS > 2); ii) FD stenting can increase from 75 to 90% the proportion of patients with a "good outcome", defined as complete or near-complete occlusion of the aneurysm AND a good clinical outcome (mRS ≥ 2) at one year, as compared to the best conventional option. The FIAT study provides a scientific and ethical context to care for patients eligible for flow-diversion therapy.

Intraventricular hemorrhage secondary to intranidal aneurysm rupture-successful management by arteriovenous malformation embolization followed by intraventricular tissue plasminogen activator: case report

BACKGROUND AND IMPORTANCE

Intraventricular hemorrhage related to arteriovenous malformation (AVM) rupture is associated with significant morbidity and mortality. Intraventricular tissue plasminogen activator (tPA) has been used to treat spontaneous intraventricular hemorrhage. We demonstrate the successful application of endovascular occlusion to seal the rupture site of an AVM followed by intraventricular tPA.

CLINICAL PRESENTATION

A 32-year-old woman presented with a right frontoparietal parasagittal AVM abutting the motor cortex. The AVM was diagnosed when the patient was 13 years old, and she initially underwent conservative management. At the age of 30, the patient suffered an intracranial hemorrhage, leaving her with left hemiparesis. After rehabilitation, the patient regained ambulation; however, she remained spastic and hyperreflexic on the left side. Two years after her major hemorrhage, she presented for elective treatment of her AVM. The patient was advised to undergo staged embolization before surgical resection of her AVM. The initial embolization was uneventful. A second embolization was complicated by intraventricular hemorrhage and coma. The patient was treated with placement of an external ventricular drain followed by embolization of intranidal aneurysm. After embolization of the intranidal aneurysm the ruptured, the patient was treated with intraventricular tPA. The patient had rapid clearance of the intraventricular hemorrhage and significant improvement in her neurological examination, following commands 24 hours later and returning almost to baseline.

CONCLUSION

This case demonstrates the feasibility of treating AVM-related intraventricular hemorrhage with tPA if the rupture source can be confidently sealed interventionally. This strategy can be lifesaving but needs further study to ensure its safety.

Influence of different computational approaches for stent deployment on cerebral aneurysm haemodynamics

Cerebral aneurysms are abnormal focal dilatations of artery walls. The interest in virtual tools to help clinicians to value the effectiveness of different procedures for cerebral aneurysm treatment is constantly growing. This study is focused on the analysis of the influence of different stent deployment approaches on intra-aneurysmal haemodynamics using computational fluid dynamics (CFD). A self-expanding stent was deployed in an idealized aneurysmatic cerebral vessel in two initial positions. Different cases characterized by a progression of simplifications on stent modelling (geometry and material) and vessel material properties were set up, using finite element and fast virtual stenting methods. Then, CFD analysis was performed for untreated and stented vessels. Haemodynamic parameters were analysed qualitatively and quantitatively, comparing the cases and the two initial positions. All the cases predicted a reduction of average wall shear stress and average velocity of almost 50 per cent after stent deployment for both initial positions. Results highlighted that, although some differences in calculated parameters existed across the cases based on the modelling simplifications, all the approaches described the most important effects on intra-aneurysmal haemodynamics. Hence, simpler and faster modelling approaches could be included in clinical workflow and, despite the adopted simplifications, support clinicians in the treatment planning.

Neuroform stent-assisted coiling of unruptured intracranial aneurysms: short- and midterm results from a single-center experience with 68 patients

BACKGROUND AND PURPOSE

Intracranial stent placement assists in the coiling of wide-neck aneurysms and aids in reconstructing and protecting the parent artery. In this study, we analyze our experience in the use of the Neuroform system.

MATERIALS AND METHODS

Records of patients treated with a Neuroform stent from June 2003 to September 2007 were retrieved from a data base for analysis of population characteristics, occurrence of complications, and acute and midterm angiographic results.

RESULTS

Sixty-eight patients harboring 76 aneurysms located primarily in the anterior circulation were treated. There were 5 cases (6.6%) of clot formation after deployment (1 with a permanent neurologic deficit), 1 case of perioperative stent displacement with hemorrhage, and 5 cases (6.6%) of transient neurologic deficit due to thromboembolic events. The morbidity-mortality rate at discharge was 2.9%. One patient presented with a delayed in-stent thrombosis, and 3 others, with silent stenosis. Twenty-four aneurysms (31.6%) were completely occluded in the initial embolization. However, a marked increase in the occlusion rate was observed, with 44 of the 68 aneurysms (64.7%) examined at the 18-month follow-up and 26 of the 46 aneurysms (56.5%) examined in the 3-year follow-up presenting with complete occlusion. At the end of the study, a neck remnant was present in 6 aneurysms (13%) and a residual sac, in 7 (15.2%). Mean follow-up time was 25.7 months.

CONCLUSIONS

The present series demonstrates the relative safety and feasibility of the Neuroform stent-assisted coiling technique, which seems to provide better results over coiling alone for wide-neck aneurysms. Angiographic results improve with time due to progressive thrombosis of the aneurysm.

In vitro study of near-wall flow in a cerebral aneurysm model with and without coils

BACKGROUND AND PURPOSE

Coil embolization procedures change the flow conditions in the cerebral aneurysm and, therefore, in the near-wall region. Knowledge of these flow changes may be helpful to optimize therapy. The goal of this study was to investigate the effect of the coil-packing attenuation on the near-wall flow and its variability due to differences in the coil structure.

MATERIALS AND METHODS

An enlarged transparent model of an ACA aneurysm was fabricated on the basis of CT angiography. The near-wall flow was visualized by using a recently proposed technique called Wall-PIV. Coil-packing attenuation of 10%, 15%, and 20% were investigated and compared with an aneurysmal flow without coils. Then the flow variability due to the coil introduction was analyzed in 10 experiments by using a packing attenuation of 15%.

RESULTS

A small packing attenuation of 10% already alters the near-wall flow significantly in a large part of the aneurysmal sac. These flow changes are characterized by a slow flow with short (interrupted) path lines. An increased packing attenuation expands the wall area exposed to the altered flow conditions. This area, however, depends on the coil position and/or on the 3D coil structure in the aneurysm.

CONCLUSIONS

To our knowledge, this is the first time the near-wall flow changes caused by coils in an aneurysm model have been visualized. It can be concluded that future hydrodynamic studies of coil therapy should include an investigation of the coil structure in addition to the coil-packing attenuation.

Clinical and angiographic long-term follow-up of completely coiled intracranial aneurysms using endovascular technique

Object

The anatomical evolution and clinical outcome of completely coiled intracranial aneurysms after endovascular embolization have rarely been studied separately. From their prospective database, the authors reviewed follow-up angiography and clinical outcome of 87 patients whose aneurysms were designated as 100% obliterated on immediate postembolization angiography.

Methods

Ninety-one aneurysms (56 ruptured and 35 unruptured) in 87 patients were included in this study. Clinical outcome was evaluated using the Glasgow Outcome Scale. Follow-up angiographic findings were assessed and categorized as 1 of the following: no recanalization, recanalization with a neck remnant, or recanalization with a body remnant. For statistical analysis, the recanalization rate was correlated with: clinical presentation; the largest aneurysm diameter, aneurysm neck size, and dome-to-neck ratio; aneurysm location; and use of special techniques such as usage of a surface modified coil, balloon remodeling technique, or stent.

Results

At the latest clinical evaluation (mean 34.3 months), 81 (93.1%) of the 87 patients (91 aneurysms) had good clinical outcomes (Glasgow Outcome Scale Score 5). The procedure-related morbidity rate (permanent neurological deficit) was 2.3% (2 of 87), and there were no procedure-related deaths. On the latest follow-up angiography (mean 26.4 months), the recanalization rate was 26.4% (24 of 91 aneurysms): 16 (17.6%) with neck remnants and 8 (8.8%) with body remnants. The neck size of the recanalized aneurysms was statistically significantly larger than that of the nonrecanalized aneurysms (p = 0.006), and aneurysms with wide necks (≥4 mm) had a higher recanalization rate than those with a narrow neck (< 4 mm) (p = 0.002). There was no bleeding after endovascular treatment during the follow-up period.

Conclusions

Completely coiled aneurysms after endovascular embolization demonstrated good clinical outcome, and there was no bleeding episode after endovascular treatment; however, there was a relatively high recanalization rate.

Neurovascular modeling: small-batch manufacturing of silicone vascular replicas

BACKGROUND AND PURPOSE

Realistic, population based cerebrovascular replicas are required for the development of neuroendovascular devices. The objective of this work was to develop an efficient methodology for manufacturing realistic cerebrovascular replicas.

MATERIALS AND METHODS

Brain MR angiography data from 20 patients were acquired. The centerline of the vasculature was calculated, and geometric parameters were measured to describe quantitatively the internal carotid artery (ICA) siphon. A representative model was created on the basis of the quantitative measurements. Using this virtual model, we designed a mold with core-shell structure and converted it into a physical object by fused-deposit manufacturing. Vascular replicas were created by injection molding of different silicones. Mechanical properties, including the stiffness and luminal coefficient of friction, were measured.

RESULTS

The average diameter, length, and curvature of the ICA siphon were 4.15 +/- 0.09 mm, 22.60 +/- 0.79 mm, and 0.34 +/- 0.02 mm(-1) (average +/- standard error of the mean), respectively. From these image datasets, we created a median virtual model, which was transformed into a physical replica by an efficient batch-manufacturing process. The coefficient of friction of the luminal surface of the replica was reduced by up to 55% by using liquid silicone rubber coatings. The modulus ranged from 0.67 to 1.15 MPa compared with 0.42 MPa from human postmortem studies, depending on the material used to make the replica.

CONCLUSIONS

Population-representative, smooth, and true-to-scale silicone arterial replicas with uniform wall thickness were successfully built for in vitro neurointerventional device-testing by using a batch-manufacturing process.

Endovascular Treatment of Intracranial Wide-Necked Aneurysms with GDCs Combined with Balloon or Stent

This article introduces our experience in embolizing wide-necked intracranial aneurysms with GDCs combined with balloon or stent. Fifty-five patients with wide-necked intracranial aneurysms (aneurysm neck ranged 2.1-7.0 mm, body/neck ≤2) underwent embolizing treatment with GDCs combined with balloon or stent. Twenty patients were treated with balloon technique. Only one complication occurred when one loop of a coil herniated into the parent artery after the GDC were detached, but no parent artery obstruction occurred. One patient died because from aneurysm rupture caused by herniation of the balloon through the over wide neck into the aneurysm during inflating. Thirty-five patients were treated with the stent technique. Five aneurysms were treated using a stent alone. Two of the five aneurysms could not be recognized from DSA after the stents were released (three and six month follow-ups showed no recurrence), one of the five ruptured leading to the patient's death two weeks after the operation. There was no aneurysm recurrence seen by DSA in the post operative follow-up of six to 12 months. GDCs combined with balloon or stent techniques are safe and effective in treatment of wide-necked intracranial aneurysms.

The effects of stenting and endothelial denudation on aneurysm and branch occlusion in experimental aneurysm models

BACKGROUND

Stents are increasingly used in the endovascular treatment of intracranial aneurysms. We studied the effects of stenting and endothelial denudation on aneurysm and branch vessel occlusion.

METHODS

Bilateral lingual bifurcation venous pouch aneurysms were created in eight dogs, surgically scraping the aneurysmal endothelial lining on one side. Both arteries were immediately stented using balloon-expandable stents. In four other dogs, a wide-neck carotid bifurcation aneurysm was created, with the vein pouch denuded or not (n=2 each), followed by immediate stenting. Results were compared using angiography and pathology at 10 days (n=2), 10 (n=8), and 20 weeks (n=2). Branch occlusion between initial and final angiograms was recorded. Pathological evaluation of aneurysms was studied, with attention to neointima formation at the aneurysm ostium and around branch vessel origins.

RESULTS

All stented and denuded lingual aneurysms were obliterated compared with two of eight lingual aneurysms that were stented alone (P=.007). None of the carotid bifurcation aneurysms became obliterated (0/4), but denuded aneurysms showed partial thrombosis (2/2). Of 68 total stent-covered branches, 5 (7%) were occluded and 17 (27%) had altered angiographic flow.

CONCLUSIONS

Stenting led to suboptimal results in the presence of an intact endothelial layer. Endothelial denudation can promote aneurysm occlusion when combined with stenting.

Effects of stenting the parent artery on aneurysm filling and gene expression of various potential factors involved in healing of experimental aneurysms

SUMMARY

Intracranial stents are increasingly used in the endovascular treatment of aneurysms, but very little is known regarding their effect on the cellular and molecular evolution of aneurysms. Bilateral venous pouch lateral wall carotid aneurysms were created in 20 dogs. All dogs then underwent angiography and balloon-expandable stenting of one aneurysm four to six weeks later. Fifteen dogs underwent aneurysm harvesting at one day (n=3), four days (n=4), seven days (n=3), and 14 days (n=5) for mRNA expression analysis, using axial sections taken from the aneurysm neck and fundus for RTPCR amplification of four cytokines or growth factors: TNF-a, TGF-b1, MCP-1, and PDGFBB; two adhesion molecules: VCAM-1 and PECAM-1; five matrix modifying agents; MMP- 2, 9, TIMPs 1, 3, 4, and two cellular markers: CD34 and a-SMA. Five other dogs, sacrificed at 12 weeks, were examined for extent of filling of the aneurysm neck with organized tissue and for neointima formation at the aneurysm ostium. Angiography was performed prior to sacrifice in all animals, and compared with initial studies. Eleven out of 20 stented aneurysms showed a favorable angiographic evolution, while none of the 20 nonstented aneurysms improved (p=0.001). Pathology showed partially occluded aneurysms, with neointima formation around the stent struts.Observed trends in mRNA expression, that stenting increased expression of genes involved in organization and neointima formation, agreed with experimental hypotheses, but differences between stented and non-stented aneurysms did not reach statistical significance. Parent vessel stenting was associated with angiographic improvement of aneurysm appearance. Modifications in mRNA expression patterns following stenting deserve further study to better establish potential molecular targets to promote aneurysm healing.

Giant Intracranial Aneurysms: Endovascular Challenges

THE TREATMENT OF giant aneurysms remains a formidable challenge for endovascular and surgical strategies. The use of endovascular techniques in a deconstructive (e.g., parent vessel occlusion) and reconstructive (e.g., stent coiling) methodology is reviewed. The results of endovascular coiling as a primary therapy for giant aneurysm occlusion have been disappointing. Hunterian strategies have had more success in published series, but recent developments in coil, glue, and stent technology show great promise in allowing parent vessel reconstruction as a primary endovascular target, with acceptable morbidity, mortality, and durability. A literature review of giant aneurysm endovascular treatment strategies was undertaken after 1994, when Guglielmi detachable coils were approved by the Food and Drug Administration. Where possible, follow-up, durability, and occlusion rates are also reviewed.

Follow-up of Treated Aneurysms: the Challenge of Recurrences and Potential Solutions

Angiographic recurrences after endovascular treatment of aneurysms with platinum coils are frequent, but hemorrhages are unusual. Recurrences are more frequent in patients with large wide-necked aneurysms, when the initial occlusion is incomplete, and when patients are treated after subarachnoid hemorrhage. Although many occur early on, they can appear years after treatment. None of the recent devices has been proven effective in improving long-term results. A rigorous scientific approach, including randomized trials, is imperative to forward progress in this field.